Efforts in the design of integrated circuits for radio frequency (RF) communication systems generally focus on improving performance, reducing cost or a combination thereof. One area of increasing interest relates to conversion of signals, such as from analog-to-digital or digital-to-analog. As communications systems become increasingly complex, increased resolution is required in the signal conversion process. The expense of signal conversion components increases dramatically with the required resolution of the converter.
The present transmission model for GSM (Global Standard for Mobile Communications) and WCDMA (Wideband Code Division Multiple Access) requires multiple carriers to be fed to a number of antennas within associated with a given base station. Generally, each antenna will have one or more associated transceivers that provide signals for broadcast or process received signals. For example, one or more digital exciters can generate digital carrier signals, convert them to an analog format, and provide them to an associated antenna for broadcast.
A typical GSM base station can have a service area divided into three sectors, each transmitting a number of carriers. For example, a high capacity sector might transmit eight full duplex carriers. Each sector can include two or more antennas, some of which can only receive signals. Each antenna includes at least one transceiver unit. Generally, the peak demand for the entire base station will employ a subset of the carriers. A base station with eight carriers per sector may use only sixteen of the twenty-four carriers at peak demand, but the demand is spread across the sectors unevenly, in a time dependent manner. Even at peak demand, nearly one-third of the digital processing capacity of the base station remains idle. If each carrier is supplied by its own transmitter and receiver, then a significant amount of hardware, including the expensive power amplifiers are idle at any time.
It has been determined that a large portion of the expense associated with a multi-carrier base station receiver within a GSM or WCDMA system is represented by the signal conversion components (e.g., analog-to-digital converters and digital-to-analog converters) and the associated digital processing components. Thus, the idle components within the base station represent a significant and unnecessary expense. Unfortunately, each sector will likely experience traffic peaks at various times throughout a period of usage, such that a certain proportion of the components will remain idle.